Stellar Molecules

To the Editors:

I enjoyed Roald Hoffmann’s Marginalia column “The Thermodynamic Sinks of this World” in your July–August issue. It was a different take on abiogenesis—the origin of life—and the far-from-equilibrium state in which we now find ourselves.

One minor error was incorporated when Hoffmann states, “From a chemist’s point of view, the surface or interior of a star…is boring—there are no molecules there.” Surprisingly, the surface of the Sun (called the photosphere) is relatively cool. Although the solar corona can reach temperatures of 5 million kelvin—and the core’s estimated temperature is three times that—the photosphere is, oddly, a “cool” 6,000 kelvin. This is cool enough to allow molecular species and molecular fragments to exist.

David NalepaCleveland, OH

Dr. Hoffmann responds:

I was mistaken in implying that the surfaces of stars are too hot for molecules to exist. For instance, evidence for H2O on the Sun was adduced by L. Wallace and others in a study published in Science in 1995. Evidence for H2 in white dwarf atmospheres was demonstrated by S. Xu, M. Jura, D. Koster, B. Klein, and B. Zuckerman in a 2013 publication in Astrophysical Journal Letters. And molecules are found in abundance in stellar ejecta.